Movement of 14 C-labeled Assimilates into Kernels of Zea mays L

Abstract

Basal tissue of developing maize kernels was examined by light micros-copy and by scanning and transmission electron microscopy. Plasmodes-mata occur in pedicel and endosperm parenchyma but were not seen between the placento-chalazal cells and basal endosperm transfer cells. A layer of nonceliular material separates the transfer cells from the placento-chalazal cells. Microautoradlography of "C-labeled assimilates entering the kernels revealed that incoming sugars are not confined to the apoplast, but rather are present in the cytoplasm and vacuoles of pedicel and endosperm cells. No specific accumulation of radioactivity was seen in any particular tissue, although at later sampling times, a higher grain density in the pedicel than the endosperm indicated a general buildup of sugars in the pedicel. A possible model for sugar movement into developing kernels is discussed.